To diminish wear in tribological systems it is not always necessary to provide the entire surface with a wear resistant layer. Depending on the application it is sufficient to harden locally the load carrying areas which are subjected to wear. Such areas can be treated properly by a laser, either totally or partially. This paper describes the effects of laser line hardening on the wear behaviour of carbon steel AISI 1045 against ball bearing steel AISI 52100. It is shown that the wear resistance of carbon steel AISI 1045 can be improved considerably by line hardening the surface. The wear resistance of the laser line hardened surfaces is comparable with that of carburised steel AISI 1045. However, the properties of the laser line hardened areas determine the wear behaviour of the entire system. Furthermore, the experimental work indicates that the type of heat treatment, carried out prior to line hardening in order to improve the microstructure of the steel, has no significant effect on the wear behaviour of the tribological system.
In sliding friction experiments, performed with lubricated concentrated contacts macroscopically operating in the lubricants’ liquid-state regime, the existence of micro-EHL has been shown. With the measuring method used, the lubricants’ limiting shear stress τ1 or the ratio of the limiting shear stress with pressure, τ1/p, can easily be obtained.
Results are presented of investigations of the running-in period in reciprocating sliding of a semicrystalline polymer, Nylon 6.6, on metal. A correlation was established between the changes in transfer film geometry and both the friction coefficient and the wear rate variations during a single stroke, as well as with sliding time. The role of wear products in ~nn~g-in was found to be the determin~g factor. In order to avoid any unspecified influence of frictional heat variation on the sliding process, the counter specimen temperature was kept constant. Significant correlations, between both local and mean coefficients of friction and local and total areas of transfer film respectively, were found. The latter relation shows the existence of two different types of running-in process which depend on whether, initially, adhesive or abrasive wear mechanisms prevail. In both cases, the building up of the transfer film together with roll-like wear particles create several types of interactions between the rubbing bodies. These interactions, subsequently called subprocesses, have their own different specific coefficients of friction and can exist on the sliding track solely or in combination. They also change their distribution over the track and finally create a variation in the mean friction coefficient with time. This variation is expressed as a function of the total area fraction of transfer film spreading with time. It is also shown that changes in wear rate coincide with variations in mean friction coefficient. The presented model can also be extended qualitatively to other semicrystalline polymers.
Friction experiments are performed on lubricated concentrated contacts (LCCs) to obtain the transitions EHL-ML and ML-BL as a function of the operational conditions under which these contacts operate. A transition diagram is developed to determine the lubrication mode of an LCC as a function of the operational conditions. In this investigation the LCCs operated macroscopically in the lubricants' liquid state regime.In lubricated concentrated contacts, operating in regime I of the IRG transition diagram,l three modes of lubrication can be
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